The invention relates to orthodontic apparatus in general, and more particularly to improvements in orthodontic apparatus for the application of directional force to one or more teeth of the upper or lower row of teeth in order to tip, upright or torque mal-occluded or otherwise misriented or improperly positioned teeth. Still more particularly, the invention relates to improvements in applicators of directional force to posterior mandibular or maxillar teeth.
It is often necessary to change the orientation and/or the position of certain teeth, particularly of the first or second molar at one or both sides of the upper or lower row of teeth. For example, such treatment is necessary to eliminate mal-occlusion of grinding teeth and to establish a so-called angle class I relationship. In accordance with a presently known proposal, a directional force applicator includes a substantially U-shaped inner arch which acts upon the posterior teeth and a substantially U-shaped outer arch which is affixed (e.g., welded) to the inner arch in the region of the lips. The directional force which is necessary for the so-called distalization of selected posterior teeth is supplied by an elastic cervical strap. The ends of the strap are connected to hook-shaped end portions of the outer arch. The latter transmits directional force to the inner arch the end portions of which extend into sleeves provided on collars surrounding the misoriented posterior teeth. The major part of the outer arch is located outside of the mouth and its median portion applies directional force to the immediately adjacent median portion of the inner arc. The aforementioned collars are cemented to the misoriented posterior teeth. Actual application of directional force to the sleeves (and hence to the respective collars) takes place by way of stops which are provided on the end portions of the inner arch and abut the respective sleeves when the inner arch is properly positioned in the mouth of the wearer.
When the just described conventional directional force headgear is to be put to use, the curvature of the inner and outer arches must be properly selected by the orthodontist to ensure the desired change of orientation of selected posterior teeth. Such directional force headgear is not suitable to change the orientation of different sets of teeth. Thus, if the dentition of a person requiring orthodontic treatment includes two or more pairs of misoriented teeth, such person must be furnished with two or more discrete pieces of directional force headgear. Moreover, conventional headgear can be used only to change the orientation of posterior teeth in the upper jaw because the utilization of a neck strap for arches which are to apply directional force to molars or bicuspids forming part of the lower row of teeth is likely to damage the joints between the upper and lower jaws.
Results of numerous experiments with conventional directional force headgear, including those known as hook-on headgear (such as straight pull headgear, high pull headgear and low pull cervical headgear) and those known as face bow headgear (such as modified high pull for face bow, variable pull headgear for face bow and padded cervical neck straps for face bow), indicate that the utilization of headgear results in a desirable change of orientation and/or location of selected teeth only if the applicator is used, without interruption, for not less than ten hours day after day. As a rule, orthodontists recommend to use the applicator for periods of 12-14 hours per day. Thus, the applicator must be in place while the patient is asleep as well as for several hours while the patient is awake and out of bed. This presents serious problems because many persons are incapable of falling asleep or remaining asleep while being fitted with a conventional headgear including an inner arch, an outer arch and a cervical strap or another extraoral directional force applying device. Moreover, the wearer of conventional headgear is prone to injury if the extraoral directional force applying device becomes detached from the hooks at the ends of the outer arch, irrespective of whether such detachment takes place while the wearer is awake and out of bed or while the wearer is asleep.
Another drawback of conventional headgear is that a substantial part thereof is readily visible and constitutes a cause of embarrassment to many wearers. This is a frequent cause of non use of such headgear or of use with frequent interruptions which, in turn, adversely affects the results of treatment and can render the treatment: useless.
Attempts to avoid the drawbacks of aforediscussed conventional headgear with extraoral direction force applying means include the provision of intraoral directional force applicators wherein the directional force is furnished by pairs of magnets. The magnets of each pair tend to repel each other to thereby urge selected teeth in a desired direction. A drawback of such intraoral applicators is that they must remain in a wearer's mouth for extended periods of time, normally several weeks. This can affect the bone tissue and prevents the wearer from properly cleaning her or his teeth during the entire period of treatment. Still further, conventional intraoral directional force applicators are expensive because each such applicator must be individually fitted to ensure satisfactory changes of orientation and/or location of selected teeth, i.e., it is not possible to mass-produce such intraoral applicators and the wearer must visit an orthodontist whenever the applicator is to be inserted into or removed from the mouth.